The invention relates to a method and a device for controlling and regulating a coupling of a motor vehicle transmission in which an electronic control unit determines the behavior of the coupling by means of a regulating circuit.
In the sense of the invention, by coupling a starting clutch is to be understood. Under the designation fall clutches mounted between an internal combustion engine and an automatic transmission, lock-up clutches and also clutches integrated in the automatic transmission which can be used both to start and as a selector clutch.
A method for controlling a starting clutch has been disclosed, e.g. in DE 44 09 122 A1. Here the starting control comprises two phases. In a first phase, the input rotational speed of the clutch is brought to a theoretical rotational speed, wherein the theoretical rotational speed is established from the drivers performance standard or the gradient and a driving activity. In the second phase, the difference between the input and the output rotational speeds of the clutch is reduced to zero according to a theoretical value curve. DE 39 37 976 A1 disclosed a method for regulating the clutch which serves to neutralize vibration. The slip of the clutch is modified, according to a revolution uniformity determined on the transmission output. From EP 0 214 989 B2, in turn, is known the use of a clutch integrated in the automatic transmission as a starting element. Departing from the above described prior art, the problem on which the invention is based is to develop it with regard to the multiple utilization of a single coupling in combination with an automatic transmission.
According to the invention, the problem is solved by the objects of the independent claims. It is advantageous that a single regulating circuit is exclusively used for control and regulation of the coupling during three operation states. The regulated quantity corresponds to the actual value of the differential rotational speed of the coupling. The three operational states correspond to a starting operation as a first state, to the driving with constant ratio as a second state, and to a third state which exists when either a gear shift under load or a change of ratio from a first to a second step ratio of an automatic transmission is initiated, the first gear shift under load being advantageously used in an automatically power shiftable stepped transmission and the change or ratio in an automatic stepped transmission with traction interruption when gear shifting for a motor vehicle.
In the case of an overlapping gear shift for a gear shift under load, an adequate regulating circuit, hereinafter designated as second regulating circuit, determines the behavior of the engaging and disengaging couplings. Such a method is known, e.g. from DE 44 24 456 A1. During the gear shift under load, the coupling is influenced as a result of the rotatory masses to be retarded or accelerated. For this case, that is, the third state, it is proposed, according to claim 2, that the first and second regulating circuits are interconnected, via an uncoupling network, wherein the uncoupling network has first and second signal paths. As states in claim 4, the second acts upon the first regulating circuit during the gear shift under load exclusively during phase load take up, gradient breakdown and closing. Thus, the advantage obtained by the uncoupling network is that the two controllers do not oppositely influence each other during operation.
For all three states, the theoretical value of the differential rotational speed of the coupling is determined from the addition of a theoretical value offset and a gear-dependent differential rotational speed of the coupling. According to claim 3, the gear-dependent differential rotational speed is determined for a starting gear of the automatic transmission via a first characteristic field. The gear-dependent differential rotational speed for non-starting gears, such as the fifth gear of the automatic transmission, is determined via second characteristic fields, as described in claim 14. Both the first and the second characteristic fields each show a coordination of performance standard of the driver and the output rotational speed of the coupling. The reversal between the first and the second characteristic fields occurs during the gear shift under load of the automatic transmission. The second characteristic fields are, according to claim 17, configured so that an increased theoretical value of the rotational speed difference results at a vehicle speed lower than a limit value. An active protection against stalling for non-starting gears, that is, the fourth and fifth gears, for example, hereby is attained.